The objective was to identify the best-validated scale for assessing oral pharmacological adherence in oncology patients. A bibliographic search was performed in MEDLINE via Ovid, EMBASE, CENTRAL and LILACS. We included all studies in which a validation of adherence scales to oral pharmacological treatment was performed in oncology patients older than 18 years without gender distinction. We excluded studies that included newly diagnosed patients. No statistical analysis was performed due to the nature of the study. A total of 4609 studies were found. After screening, six studies were selected for qualitative analysis. In the analysis of the six included studies, a total of 855 patients older than 18 years with oncological diagnoses were found. Two of the studies, Bagcivan et al. and Amorim et al., used scales that show acceptable validity and reliability to adequately measure adherence to pharmacological treatment in each of the patients. In this way, the quality of patient care and success in pharmacological treatments can be guaranteed. According to the results obtained in the evaluation of biases and analysis of psychometric properties, the best-validated scales are as follows: Adherence Determinants Questionnaire (ADQ) (Brazilian version) and the Oral Chemotherapy Adherence Scale (OCAS). These are valid, reliable and useful scales that can be adapted to any cultural context.